Generally, a lighting apparatus used for implementing a certain forward eyesight when driving a vehicle in the night or a bad weather condition is classified into a low angle headlight and a high angle headlight. In an integration type headlight, a low angle headlight filament and a high angle headlight filament are integrally formed in one lamp, and in a separation type headlight, a low angle headlight lamp and a high angle headlight lamp are separately formed in one lamp. The integration and separation type headlights each include one low angle headlight filament and one high angle headlight filament in one lamp, respectively. The on and off operation is simply performed in such a manner that beam is lighted with a fixed luminous intensity and at a high and low lighting angle based on a switch operation by a driver.
According to the Korea Standard (KS) and a vehicle safety standard, the headlight has a beam luminous intensity from above 15000 cd (candela) to 125000 cd in maximum. The concurrently turned-on integration type conversion beams have a luminous intensity in a range from 12000 cd in minimum to 120000 cd in maximum. According to a vehicle lighting safety standard, a maximum lighting distance is within 15 m in a forward direction, and a low beam is within 10 m. With the above standard, it should be possible to perceive and check a certain obstacle in a lighting range.
At an initial stage, the headlight is formed of lens, bulb, and reflection mirror. Recently, a shield beam bulb formed in an integration type is generally used. A high and low angle headlight integration type headlight or a high headlight and low headlight are provided in a separation type in a pair in the left and right sides, respectively. In the above high and low angle headlight integration type headlight, a low angle headlight filament and a high angle headlight filament used for a headlight of a conventional vehicle are integrally formed in one lamp.
The lamp of the headlight is formed of an alloy filament that is formed of tungsten and molybdenum as a main material and is mixed with a metallic material having a low resistance ratio for the purpose of preventing a power loss by decreasing a load of heating material, increasing brightness and extending a life span by preventing an oxidation of filament. In the conventional art, a space layer between a filament and an outer glass wall is formed of a vacuum layer. Recently, a load resistance of current is increased by injecting an alternative gas into a vacuum layer, so that a heating efficiency of a filament is increased, and a lighting light is increased.
In the integration type and separation type, the headlight of vehicle is separated into an opponent beam (capable of preventing dazzling by an opponent vehicle in such a manner that an optical axis is oriented in a lower direction, namely, a low headlight), and a running beam (in which an optical axis is lighted far in a horizontal direction, namely, a high angle (or horizontal) headlight).
According to the vehicle luminous intensity safety standard law, the headlight of a conventional vehicle has a lighting luminous intensity difference more than at least 10 times based on the kinds of vehicles and a design performance. The headlight is designed to light at a uniform luminous intensity and a fixed lighting angle based on a night eyesight of a driver who has a good health for thereby easily recognizing an existence of obstacle or a movement based on a good road condition. Therefore, the driving apparatus of a headlight of a vehicle is designed to light only an opponent direction beam capable of lighting a low angle beam or a high angle beam or a running beam capable of concurrently lighting a high and low angle beam based on a switch operation of a headlight by a driver.
Since the headlight is used for obtaining a certain forward visual field during the night or bad weather driving, the headlight is a very important apparatus for a vehicle.
In a conventional art, there is a difference more than 10 times in a performance based on a design in a headlight having a common vacuum lamp, halogen lamp and HID (High Intensity Discharge) lamp that are formed in a fixed luminous intensity structure or a fixed angle lighting structure. The conventional headlight is designed to light at the same luminous intensity even when a driver drives in a rainy night or on a sequestered road in which it is impossible to obtain a satisfied luminous intensity for a forward direction clean visual field and even when a driver who has a night blindness drives during the night.
Therefore, in the above state, since a driver drives based on a sensitive method, not based on a visual field method, there may be a serious accident in safety driving of a vehicle.
The stop distance of a running vehicle is determined by summing a perception reaction distance (needed for a driver to perceive a certain danger, and a brake starts to operate) and a braking distance (needed for a vehicle to stop after a brake starts operating). The headlight of vehicle should be designed to light during at least stop distance based on the speed of a vehicle.
For example, in the case that a vehicle runs at 20 km/h, the stop distance is 9 m by summing the perception reaction distance of 6 m and the braking distance of 3 m, and in the case that the vehicle runs at 40 km/h, the stop distance is 22 m by summing the perception reaction distance of 11 m and the is braking distance of 11 m, and in the case that the vehicle runs at 60 km/h, the stop distance is 44 m (perception reaction distance of 17 m+braking distance of 27 m), and in the case that the vehicle runs at 80 km/h, the stop distance is 76 m (perception reaction distance of 22 m+braking distance of 54 m), and in the case that the vehicle runs at 100 km/h, the stop distance is 112 m (perception reaction distance of 28 m+braking distance of 84 m).
In addition, in a reaction processing procedure of the sudden braking needed after a driver perceives a certain dangerous situation, the reflection time (required to react with a sound of “O My!”) is 0.7˜0.8 seconds in the case of the sudden braking, and the reaction time is 2.5˜3.0 seconds in the common braking operation. The conventional low angle headlight is designed without considering the stop distance based on the speed and the reaction time based on the sudden braking. Namely, the conventional low angle headlight is formed in a fixed type structure capable of only lighting an area within a forward 15 m range with a fixed luminous intensity.
Therefore, in the case of a vehicle having a HID lamp when the vehicle runs in an area having a bright surrounding, the headlight has over luminous intensity, so that the power is unnecessarily consumed. In the case that a driver drives a vehicle during a bad weather in which a visual field is very limited in a rainy night or a driver having a night blindness drives a vehicle having a vacuum lamp or halogen lamp, it is impossible to obtain a proper brightness for a safety driving. Even when the headlight is turned on, the forward concentration of the driver is decreased.
In addition, the conventional low angle headlight is designed to have a main observing point of a forward 15 m distance. Therefore, when the vehicle runs at an economical speed of 60 km/h with a stop distance of 44 m (perception reaction distance of 17 m+braking distance of 27 m) and at a speed of 80 km with a stop distance of 76 m (perception reaction distance of 22 m+braking distance of 54 m), since it is impossible to perceive a certain thing existing within a stop distance, even when the headlight is turned on, it is impossible to perceive a forward obstacle within a stop distance and a reaction time based on a sensitive driving for thereby directly causing a traffic accident.
In the conventional vehicle, when the vehicle turns left or right in the night, since the headlight does not light along the intended turning direction, it is impossible for a driver to perceive a certain obstacle during the turning operation, so that there is a serious problem for implementing a safety driving.
In addition, in the case that the low angle headlight filament generally used for the headlight is disconnected, there is not a proper method for overcoming the problem during the driving. In this case, there is an inconvenient problem when exchanging the headlight. A certain danger may occur due to the lost of the lighting function.